Control system



H. E. NASON CONTROL SYSTEM Dec. 28, 1937.

Filed Aug. 7. 1936 WITNESSES:

Patented Dec. 28, 1937 PATENT OFFICE CONTROL SYSTEM Horace E. Nason,Berwyn, 111., assignor to Westinghouse Electric & Manufacturing Company,

East Pittsburgh, Pa., vania Application August 7,

6 Claims.

This invention relates to control systems for paper mill drives.

In the manufacture of paper, it is usually made in webs that are toowide for-other industries. These wide webs of paper are usually cut orslit into secondary Webs of commercial size by transferring the wide webof paper from the paper machine past a roll carrying a slitter knife andadapted to rotate therewith to winder rolls upon which the secondarywebs are wound. The slitter knife is carried by a roll driven at a speedapproximating the speed of the winder rolls upon which the secondarywebs are wound. If the speed of the roll carrying the slitter knife isreduced or falls below that of the winder rolls, the knife does not cutthe paper, but instead tears it with the result that much spoilage ofthe paper is encountered during the slitting operation. Such conditionsare more often found during the starting and stopping of the slittingoperation. This is because the rolls on which the secondary webs arewound are often started before or ac- ,celerate at a faster rate thanthe roll carrying the slitter knife. Further, in stopping the slitterand Winder drive, the roll carrying the slitter knife sometimes stopsbefore the winder rolls, with the result that the web tears as it isdragged past the stationary knife.

An object of this invention is to provide for starting and acceleratinga slitter knifeto a predetermined speed before the winder rolls arestarted.

Another object of this invention is to provide for starting andaccelerating a slitter knife to a predetermined speed before the winderrolls are started and for maintaining the slitter knife at apredetermined speed after the winder rolls are stopped.

A more specific object of this invention is the provision fortransferring a slitter motor from an exciter to a generator upon theoccurrence of predetermined voltage conditions, and to transfer theslitter motor from the generator back to the;

ing drawing, in which:

and

Figure 2 is a graph, the curves of which illustrate the control of thespeed of the slitter and Figure l is a diagrammatic view of the control)system embodying the features of this invention.

a corporation of Pennsyl- 1936, Serial No. 94,822

winder motors obtained in accordance with the teachings of thisinvention.

Referring to the drawing and Fig. 1 in particular, this inventioncomprises a slitter roll l0 carrying a knife H for rotation therewith toslit a web of paper l2 as it is transferred from a roll of paper I4 tothe winder rolls l6 and i8.

The slitter roll III is mechanically connected by means of a shaft 20 toa slitter motor 22 disposed to be electrically connected through a highresistance 26 to an exciter 28. Theslitter motor 22 is provided with ashunt field 24 disposed to be connected through a resistor to theexciter 28. The Winder rolls IE and [8 are mechanically con nectedthrough shafts 3D and 32, respectively, to compound motors 34 and 36,each of which is pro vided with a series field 38 and a shunt field 40.The compound'motors 34 and 36 are disposed to be electrically connectedto a generator 42 which is provided with a field winding 44.

In order to vary the excitation of the generator 42, a master rhecstat50 is disposed to be connected in circuit relation with the field 44.The rheostat 50 may comprise any of the well known types of rheostatsand is provided with a plurality of taps for connecting differentportions of the rheostat in circuit with the field 44. The operation ofthe rheostat for varying the excitation of the generator andconsequently the voltage delivered to the winder motors will be explained more fully hereinafter.

In order to transfer the slitter motor 22 from the exciter 28 to thegenerator 42, a relay 52 is so connected with its actuating coil incircuit with the generator 42 that upon the occurrence of predeterminedvoltage conditions the relay is actuated to disconnect the slitter motor22 from the exciter 28 and to connect it to the generator 42. A timelimit relay 54 of the type disclosed in Pat-- as No. 1,753,9 3, issuedApril 8, 1930 to w. G.

' "Cook, may her-"employed to insure the transfer the slitter/motor fromthe exciter to the gen- .ierator when the actuating coil of the relay 52is energized.

In operation, the prime mover 48 drives the exciter 28 and the generator42. ihe slitter motor is electrically connected to the exciter andaccelerated to a predetermined speed. The shtter motor circuit may betraced from the exciter through the knife switch 56, conductor 58,adjustable regulating resistor 80, the shunt field 24 of the slittermotor 22, conductorsSZ and 84 back to the exciter. When the field oi theslitter motor is energized, the start button 66 may be actuated, closinga circuit which extends from the exciter through the knife switch 56,conductors 68 and 18, actuating coil 12 of a low voltage relay 14,conductors 16 and 18 and start button 66 to through the actuating coil86 of relay 88 and the contact member I81 of the relay 52 to theenergized conductor 64. When thus energized, the relay 88 is actuated toa circuit closing position in which contact member 98 connects thearmature of the slitter motor22 to the exciter 28 to initially energizethe slitter motor. The circuit thus established may be traced from theenergized conductor 68 through resistor 26, contact member 98 of therelay 88, conductor 92, the armature of the slitter motor 22 andconductor 62 to energized conductor 68. The operating speed of theslitter motor 22 when connected to the exciter 28 is controlled by theresistor 26 which is in series with the armature of the motor. Thispredetermined speed is represented in Fig. 2 of the drawing by theordinate 0-1.

When the relay 88 is actuated to connect the slitter motor 22 to theexciter 28, a circuit is also established by contact member 96 forenergizing the magnetizing coil 96 of the time limit relay 54. Thiscircuit extends from the energized conductor 68 through contact member94 of the relay 88, magnetizing coil 96 of the time limit relay 54 andthe resistor 91 in parallel therewith, to energized conductor 16. Sincethe magnetizing force of the coil 96 is greater than the neutralizingforce of the neutralizing coil 98 of the time limit relay 54, thearmature I88 is actuated to a position where a movable contact memberI82 carried by the armature engages a contact member I84 and is held ina circuit closing position. The neutralizing coil 98 of the time limitrelay 54 is provided for effecting a substantially constant dissipationof the residual magnetism of the core member of the relay from themaximum energized condition to zero for obtaining a prompt action of thearmature I88 at any predetermined time interval in accordance with theteachings of the hereinbefore-identified Patent No. 1,753,983.

After the slitter 'motor 22 is started and accelerated to thepredetermined speed, the winder motors 34 and 38 may be connected to thegenerator 42 by actuating the bridging member I86 of the rheostat 58 toclose a circuit through the actuating coil of contactor I32. As shown inthe drawing, a movement of the bridging member I86 to the first tap ofthe rheostat establishes a circuit which may be traced from theenergized conductor 68, through resistor I88, field 44 of the generator42, bridging member I86, conductors I I8 and M2 to energized conductor68. By connecting the resistor I88 in series with the field 84, anyresidual voltage of the generator 42 is bucked down as will be morefully described hereinafter.

A further movement of the bridging member I88 to the next tap ofrheostat 58 causes segment II4 of the bridging member I86 to close acircuit which extends from the energized conductor 68 through stopbutton I28, actuating coil I22 of relay I24, conductor I26, bridgingsegment H4, contact member II5, conductors H8 and H2 to energizedconductor 64. When this circuit is closed, actuating coil I22 of relayI24 is energized to actuate the relay I24 to a circuit closing positionwhere its contact member I42 establishes a holding circuit for therelay. This circuit may be traced from the energized coil I22 throughconductor II2 to energized conductor 64.

If the bridging member I86 is actuated to the third tap of the resistor58, the segment.| I4 of the bridging member bridges conducting segmentsH6 and H8 to close a circuit which extends from energized conductor I26,through conductor I28, actuating coil I38 of contactor I32, contactmember I36 of contactorv I32, and coil I38 of relay I48 to energizedconductor 64. The energization of coil I38 of contactor I32 causes thecontactor I32 to be actuated to a circuit closing position in whichcontact members I44 and I46 connect the winder motors 34 and 36,respectively, to the arma re of the generator 42. In this position thecont; t member I48 of contactor I32 closes a circuit I hich may betraced .from energized conductor 68 through conductor I58, contactmember I48, conductor I52 and actu .ating coil I54 of relay I56 toenergized conductor 64.

circuit may be tracedfrom energized conductor 68 through contact memberI58, conductor I68, field 54 of generator 42, rheostat 58, and conductorI62 to the energized conductor 68.

In order to increase the voltage generated by the generator 42, therheostat 58 is adjusted to increase the strength of the field 44. As thevoltage generated and delivered to the winder motors increases andconsequently the speed of the motors 84 and 56 approaches thepredetermined speed of slitter motor 42, represented in Fig. 2 by theordinate 0-1, actuating coil I59 of relay 52 is energized to actuate therelay to.an energized position. In this position the contact member I6Iof relay 52 is in a circuit interrupting position and contact member I62is in a circuit closing position. 6

When the contact member I6I is actuated to its circuit interruptingposition, actuating coil 86 of relay 88 is de'energized and relay 88drops to its deenergized position in which the contact members 98 and 94interrupt the circuits from the exciter to the armature of the slittermotor and from the exciter to the magnetizing coil 96 of the time limitrelay 54, respectively. Because of the characteristics of the relay 54 apredetermined time limit is provided in which the contact members I82and I84 engage after the contact member 94 interrupts the circuit to themagnetizing coil. This period of delay is suflicient to permit contactmember I62 of relay 52 to close a circuit which extends from energizedconductor 68 through the contact members I84 and I82, ar-

mature I88, conductor I64, actuating coil I68 of Since each of themotors is connected in circuit relation with the generator, the speed ofthe motors may be controlled by adjusting the master rheostat 50 toregulate the voltage generated by the generator 42. Since the margin ofspeed at a given armature voltage of the generator between the slittermotor and the winder motors as shown in Fig. 2 is fixed by thecharacteristics of the motors, the safety margin may be maintained overa given range of speed.

Upon a decrease in speed of the winder motors through an insertion ofmore of the rheostat 50 in series with the field 44 of the generator 42,the speed of the slitter motor is decreased proportionately to the speedof the winder motors. When the voltage generated decreases and the speedof the motors is lowered to the predetermined value, the actuating coilI58 becomes deenergized and the relay 52 returns to its deenergizedposition. As the relay 52 drops to its deenergized position, contactmember I62 drops to a circuit interrupting position to interrupt thecircuit to and deenergize the actuating coil I68 of relay I'I0. When thecoil I68 is deenergized, relay "0 and its contact member I12 drop to acircuit interrupting position to disconnect the slitter motor from thegenerator. The deenergization of actuating coil I59 of relay 52 alsopermits contact member I6I of the relay to drop to a position where itestablishes an energized circuit through the actuating coil 86 of relay88 to actuate the relay to a circuit closing position in which contactmember connects the slitter motor to the exciter. Thus as the voltagegenerated and delivered to the winder motors 34 and 36 is furtherdecreased, the speed of the slitter member 32 is maintained at thepredetermined speed to cause the operation of the slitter knife I0 eventhough the winder motors stop.

In order to stop the winder motors, the bridging member I06 of therheostat 50 is actuated to a position where the bridging segment I I4bridges the segment H6 and contact member II5 of conductor IIO. In thisposition the circuit through the actuating coil I 30 of interlock I 32is interrupted and the interlock I32 drops to its deenergized positionin which the contact members I44 andI46 disconnect the motors 34 and 36,respectively, from the generator 42. When the interlock I32 is in itsdeenerglzed position, the contact member I48 interrupts the circuitthrough the coil I54 of relay I56 causing relay I56 to drop to itsdeenergized position in which contact member I58 interrupts the circuitfrom the energized conductor 64 through the field 44 of the generator42. When the interlock I32 is in its deenergized position, the contactmember I36 closes a circuit as hereinbeiore explained, which extendsfrom energized conductor I34 through the actuating coil I38 of relay I40to energized conductor 64. The relay I40 is thus actuated to its circuitclosing position in which contact members I16 and I18 connect resistorsI80 and I82, respectively, in shunt circuit relation about the motors 34and 36 to provide dynamic braking therefor.

In stopping the winder motors 34 and 36, the speed of the motors may bedecreased by actuating the bridging member I06 of rheostat 50 to itsinitial position where a circuit through the high resistor I08 iscompleted, reversing the field and bucking down any residual magnetismof the generator. The field of the generator is thus reversed from thenormal excitation direction when the winder motors are disconnected fromthe generator and for all initial starting operations of the system. Byproviding for reversing the field oi the generator, as described, thegenerator voltage is increased slowly in the proper direction as therheostat 50 is cut out of the circuit by the bridging member I06 and asmooth starting operation of the winder motors 34 and 36 is obtained.

When desired, the winder motors may be disconnected from the generatorby actuating stop button I20 to its circuit interrupting position whereit interrupts the circuit through the actuating coil I30 of thecontactor I32. The opera. tion of the contactor I32 to disconnect thewinder motors 34 and 36 from the generator 42 and to close an energizedcircuit through relay I40 to connect resistors I80 and I82,respectively, in shunt circuit relation about the winder motors 34 and36 to provide dynamic braking therefor is the same as has been describedhereinbefore.

The slitter motor 22 may be stopped at any time by depressing the stopbutton 84 to interrupt the circuit through the actuating coil I2 ofrelay I4 and to deenergize the actuating coil 86 of relay 88 todisconnect the slitter motor 2 from the exciter 28. e

In the operation of the control system as hereinbefore described it isevident that the slitter motor may be started and accelerated to apredetermined speed prior to the starting of the winder motors, andafter the, stopping of the winder motors. By this control system animproved slitting operation is obtained by maintaining a definitepredetermined minimum speed of the slitter knives. Further, it is seenthat the speed of the slitter motor varies in accordance with the speedof the winder motors for all speeds above a predetermined minimum speedand that operation of the slitter motor is insured even after the windermotors have ceased to function. This invention provides against damageto the web of the paper through a failure of the slitter motor tomaintain a, speed greater than that of the winder motors.

Although this invention has been described with reference to aparticular modification thereof, it is to be understood that other andvarious modifications thereof are possible. This invention is,therefore, not to be restricted except insofar as is necessitated by theprior art and the scope of the appended claims.

I claim as my invention:

1. In a paper mill drive, a generator having a field winding, an exciterfor the field winding, a slitter motor disposed to be connected to theexciter, a winder motor disposed to be connected to the generator, meansfor controlling the generator to control the voltage output therefrom,and means res;.onsive to predetermined voltage conditions fortransferring the slitter motor to the generator to control the speed ofthe slitter motor with respect to the speed of the winder motor.

2. In a paper mill drive, a generator having a field winding, an exciterfor the field winding, a. slitter motor disposed to be connected to theexciter, a. winder motor disposed to be connected to the generator,means for controlling the generator to control the voltage outputtherefrom, and means responsive to predetermined voltage conditions fortransferring the slitter motor from the exciter to the generator tocontrol the speed of the slitter motor with respect to the speed of thewinder motor, the said means being responsive upon failure of thepredetermined Voltage conditions to transfer the slitter motor from tothe generator after the initial energization the generator to theexciter to maintain the operation of the slitter motor at apredetermined speed.

3. In a paper mill drive, a generator having a field winding, an exciterfor the'fleld winding, a slitter motor disposed to be connected to theexciter, a winder motor disposed to be connected to the generator, meansfor controlling the excitation of the generator to control the voltageoutput therefrom and thereby control the speed of the winder motor, andmeans responsive to a predetermined voltage output of the generator fortransferring the slitter motor from the exciter to the generator tocontrol the speed of the slitter motor with respect to the speed of thewinder motor.

4. In a paper mill drive, a generator having a field winding, an exciterfor the field winding,

a slitter motor, means for connecting the slitter motor to the eirciterto initially energize the slitter motor and operate it to apredetermined speed, a winder motor disposed to be connected to thegenerator after the initial energlzation of the slitter motor, means forcontrolling the excitation of the generator to control the voltageoutput therefrom and thereby control the speed of the winder motor,'andmeans responsive to predetermined voltage conditions for transferringthe slitter motor to the generator to control the speed of the slittermotor with respect to the speed of the winder motor.

5. In a paper mill drive, a generator having a field winding, a'nexciter for the field winding, a slitter motor, means for connecting theslitter motor to the exciter to initially energize the slitter. motorand operate it ,to a predetermined speed, a winder motor disposed to beconnected of the slitter motor, means for controlling the excitation ofthe generator to control the voltage output therefrom and therebycontrol the speed of the winder motor, and means responsive topredetermined voltage conditions for transferring the slitter motor fromthe exciter to the generator .to control the speed of the slitter motorwith respect to the speed of the winder motor, the said means beingresponsive upon failure of the predetermined voltage conditions totransfer the slitter motor fromthe generator to the exciter to maintainthe operation of the slitter motor at a predetermined speed.

6. In a paper mill-drive, a generator having a field winding, an exciterfor the field winding, 9. slitter motor, means for connecting theslitter motor to the exciter to initially energize the slitter motor andto operate it to a predetermined speed, a winder motor disposed to beconnected to the generator after the slitter motor is initiallyenergized, means for controlling the voltage output from thegeneratorand thereby control the speed of the winder motor, means responsive to apredetermined voltage output for transferring the slitter motor from theexciter to the generator for increasing the speed of the slitter ,motoras the speed of the winder motor increases,

noaacjn E. NASON.

